Does BMP2 play a role in the pathogenesis of equine degenerative suspensory ligament desmitis?

OBJECTIVE: Horses afflicted with degenerative suspensory ligament desmitis (DSLD) suffer from progressive leg pain and lameness without history of trauma. DSLD is a systemic disorder caused by abnormal accumulation of proteoglycans in many connective tissues. One proteoglycan found in higher quantities in DSLD is decorin. The accumulated decorin has an abnormally glycosylated glycosaminoglycan chain in DSLD. In addition to acellular accumulations of proteoglycans foci of active fibroblasts/tenoblasts were observed in some tendons and suspensory ligaments (SLs) from DSLD cases We have hypothesized that this represents an early event in DSLD and that production of chondrogenic growth factors, such as BMP2, and/or enzyme participating in glycosylation of glycosaminoglycans is a major factor in initiation and progression of DSLD. RESULTS: Using immunohistochemistry we have identified BMP2 in these cellular foci, indicating association with proteoglycan production, but not in other cells in the tendon and SLs. In contrast, very little staining for TGFß and dermatan sulfate epimerase, an enzyme involved in glycosylation of glycosaminoglycan chains, was observed in these foci and other cells in both control and DSLD-affected tendons and SLs. Our data support our hypothesis that chondrogenic growth factors may be responsible, at least in part for progression of DSLD in horses.

A profile of morbidity and mortality rounds within resident training programs of the American College of Veterinary Surgeons.

OBJECTIVE: To describe the structure and role of morbidity and mortality rounds (MMR) in resident training programs of the American College of Veterinary Surgeons (ACVS). STUDY DESIGN: Cross-sectional analysis: survey. SAMPLE POPULATION: ACVS surgical resident program directors. METHODS: Electronic surveys consisting of 27 questions were sent to the directors of 142 ACVS resident programs. RESULTS: Forty-five (31.6%) programs completed the survey, including 24 (53.3%) from small animal programs and 21 (46.7%) from large animal programs. Thirty-two (71.1%) programs incorporated regular MMR in their training. The primary goal of these rounds was improvement of patient care (63%) and education (31%). Selection of cases was based on unexpected mortality (80%), unexpected morbidity (77.4%), teaching value (65.7%), and review of medical errors (63%). Twenty-six percent of programs reported conducting formal follow-up for topics discussed during MMR. Ninety-five percent of programs believed that MMR were valuable. CONCLUSION: MMR are commonly incorporated in surgical resident training programs. The primary objectives of these rounds are to educate residents, refine hospital medical and operational policies, and to improve patient care. The majority of residency programs view MMR as worthwhile. However, the majority of veterinary residency programs fail to follow up MMR with formal initiatives for improvement and objective outcome assessments for issues identified during MMR.

Ex Vivo Mechanical Evaluation of a Sternal ZipFix(®) Implant for Prosthetic Laryngoplasty in Horses.

OBJECTIVE: To evaluate the properties of a ZipFix(®) (ZipFix) implant in equine laryngeal cartilages. STUDY DESIGN: Ex vivo biomechanical study. SAMPLE POPULATION: Equine arytenoid (n=36) and cricoid cartilages (n=18). METHODS: Suture bites were placed in arytenoid or cricoid cartilages using a ZipFix(®) implant or a single strand of USP 5 braided polyester (TiCron™), and arytenoid and cricoid cartilages were separately subjected to single load to failure (25 N preload) or cyclic loading for 1,000 cycles, followed by single load to failure. Load, distraction, and stiffness were recorded. RESULTS: Four arytenoid-ZipFix cartilages fractured on implant placement. Under single load, arytenoid-ZipFix (n=9) failed at a greater mean load (359.01 ± 57.98 N) than arytenoid-Ticron (159.11 ± 22.98 N; n=12; P<.001). Arytenoid-ZipFix stiffness (31.32 ± 4.26 N/mm) was significantly greater than arytenoid-Ticron (13.18 ± 2.60 N/mm; P<.001). Cricoid-ZipFix stiffness (20.83 ± 3.37 N/mm) was significantly greater than cricoid-Ticron (13.6 ± 3.82 N/mm; n=6; P=.006). Under cyclic load, arytenoid-ZipFix distraction (2.53 ± 0.63 mm; n=5) was significantly less than arytenoid-Ticron (5.06 ± 1.37 mm; n=6, P=.006). After cyclic load, arytenoid-ZipFix failure load (295.16 ± 54.95 N) was significantly greater than arytenoid-Ticron (127.69 ± 32.67 N; P=.002). Arytenoid-ZipFix stiffness (35.59 ± 1.58 N/mm) was significantly greater than arytenoid-Ticron (24.10 ± 6.85 N/mm; P=.019). CONCLUSION: In arytenoid cartilages, the sternal ZipFix(®) implant was significantly stronger and stiffer compared to a single strand of Ticron. During placement of the ZipFix(®) implant, frequent arytenoid cartilage failure occurred before testing, suggesting the implant is not suitable for clinical application.

Comparison of tensile strength and early healing of acute repeat celiotomy through a ventral median or a right ventral paramedian approach.

OBJECTIVE: To compare tensile strength, failure location, and histologic features after acute repeat celiotomy through a ventral median (RVM) or a right ventral paramedian (RVP) celiotomy in horses. STUDY DESIGN: Ex vivo experimental study. ANIMALS: Adult horses (N = 18). METHODS: Twelve adult horses had original ventral median (OVM) celiotomy. Repeat celiotomy was performed 72 hours postoperatively through the original ventral median (RVM, N = 6) or a RVP (N = 6) celiotomy. Celiotomies were scored daily for edema, drainage, and dehiscence. Fourteen days after repeat celiotomy, horses were euthanatized and abdominal wall containing celiotomy(ies) were collected for biomechanical and histological evaluation. The abdominal wall of control horses (N = 6; no celiotomy) was collected for biomechanical testing. Vital sign variables, incisional edema, and histologic scores were compared using a Wilcoxon signed-rank test. Incisional fibrotic depth and tensile strength per unit length (N/cm) was compared using repeated measures ANOVA. RESULTS: RVM and RVP horses had significantly less tensile strength compared to control horses, but no differences were observed between RVM and RVP horses. No differences in healing, inflammation, infection, or necrosis of repeat celiotomies was observed, but RVP horses accumulated more fibrin and hemorrhage within the incision. RVP horses had significantly greater incisional edema scores, but incisional drainage was more frequent in RVM horses. CONCLUSIONS: Acute repeat celiotomy through a RVM incision results in similar incisional healing and tensile strength compared with repeat celiotomy through a RVP incision.

In vitro comparison of a single-layer (continuous Lembert) versus two-layer (simple continuous/Cushing) hand-sewn end-to-end jejunoileal anastomosis in normal equine small intestine.

OBJECTIVES: To compare in vitro physical and mechanical characteristics of 1-layer and 2-layer end-to-end jejunoileostomy. STUDY DESIGN: In vitro experimental study. ANIMALS: Adult horses (n = 6). METHODS: Harvested equine jejunum and ileum was used to create 1- and 2-layer end-to-end jejunoileostomy specimens. Construction time, bursting pressure, and relative lumen diameter (anastomosis diameter expressed as a percentage of the lumen diameter of adjacent jejunum and ileum) were compared. Construction time and relative lumen diameters were compared using a paired t-test. Bursting pressure for anastomoses and control jejunal segments were compared using a repeated-measure ANOVA. Statistical significance was set at P < .05. RESULTS: Mean (± SEM) construct completion times were shorter for 1 layer (21 ± 0.91 minutes) than 2 layers (26.71 ± 1.16 minutes; P = .005). Relative lumen diameters (percentage of jejunal diameter) were larger for 1 layer (77.67 ± 4.46%) than for 2 layers (69.37 ± 2.8%; P = .035). There were no significant differences in bursting pressures between the 2 groups and the control jejunum (P =.155) or relative lumen diameters (percentage of ileal diameter; P =.118). CONCLUSIONS: One-layer jejunoileostomy can be created in a shorter time and maintain a larger anastomosis luminal diameter without compromising maximum bursting pressure when compared to 2-layer jejunoileostomy.

Ileal impaction in 245 horses: 1995-2007.

The objective of this study was to identify parameters that would assist in determining the probability of a successful outcome with medical management versus surgical intervention in horses with ileal impaction. Medical records of 245 horses admitted for ileal impaction were reviewed and placed into 2 groups: medical (med) and surgical (sx) treatment. Persistence of abdominal pain, gastric reflux, frequency of analgesic administration, and 1-year survival were evaluated. There were no differences in signalment, abdominal pain, or heart rate among groups; however, significantly more sx horses had peritoneal fluid abnormalities (51%) and produced gastric reflux (62%) than did med horses (38% and 15%, respectively). Eighty-nine percent of med horses required repeated analgesic administration for successful resolution. One-year survival was 91% for sx horses and 92% for med horses. Horses with ileal impaction responsive to analgesic therapy with minimal gastric reflux are likely to be managed successfully with medical treatment. Horses with persistent abdominal pain and gastric reflux are candidates for surgery.

Degenerative suspensory ligament desmitis as a systemic disorder characterized by proteoglycan accumulation.

BACKGROUND: Degenerative suspensory ligament desmitis (DSLD) is a debilitating disorder thought to be limited to suspensory ligaments of Peruvian Pasos, Peruvian Paso crosses, Arabians, American Saddlebreds, American Quarter Horses, Thoroughbreds, and some European breeds. It frequently leads to persistent, incurable lameness and need to euthanize affected horses. The pathogenesis remains unclear, though the disease appears to run in families. Treatment and prevention are empirical and supportive, and not effective in halting the progression of the disease. Presently, the presumptive diagnosis of DSLD is obtained from patient signalment and history, clinical examination, and ultrasonographic examination of clinically affected horses, and is confirmed at post mortem examination. Presently, there are no reliable methods of diagnosing DSLD in asymptomatic horses. The goal of this study was to characterize and define the disorder in terms of tissue involvement at the macroscopic and microscopic levels. RESULTS: We examined tissues and organs from 28 affected horses (22 Peruvian Pasos, 6 horses of other breeds) and from 8 control horses. Histopathological examination revealed the presence of excessive amounts of proteoglycans in the following tissues removed from DSLD-affected horses: suspensory ligaments, superficial and deep digital flexor tendons, patellar and nuchal ligaments, cardiovascular system, and sclerae. Electron microscopy demonstrated changes in diameters of collagen fibrils in the tendon, and in smooth muscle cells of the media of the aorta compatible with increased cell permeability in DSLD-affected cells. Separation of tendon extracts by gel chromatography revealed the presence of additional proteoglycan(s) in extracts from affected, but not control extracts. CONCLUSION: This study demonstrates for the first time that DSLD, a disease process previously thought to be limited to the suspensory ligaments of the distal limbs of affected horses, is in fact a systemic disorder involving tissues and organs with significant connective tissue component. Abnormal accumulation of proteoglycans between collagen and elastic fibers rather than specific collagen fibril abnormalities is the most prominent histological feature of DSLD. Because of this observation and because of the involvement of many other tendons and ligaments beside the suspensory ligament, and of non-ligamentous tissue we, therefore, propose that equine systemic proteoglycan accumulation or ESPA rather than DSLD is a more appropriate name for this condition.

Effect of carboxymethylcellulose and hyaluronate solutions on jejunal healing in horses.

OBJECTIVE: To compare a double-layer inverting anastomosis with a single-layer appositional anastomosis, coated with either 1% sodium carboxymethylcellulose (SCMC) or 0.4% sodium hyaluronate (HA) solutions, in the small intestine of horses with respect to anastomotic healing and adhesion formation. ANIMALS: 18 adult horses. PROCEDURE: Midline celiotomy and end-to-end jejunal anastomoses were performed. In control group horses (n = 6), a double-layer inverting anastomosis coated with sterile lactated Ringer's solution was performed. In treatment group horses, a single-layer appositional anastomosis was performed that was coated with 1% carboxymethylcellulose solution (SAA + SCMC group horses, 6) or 0.4% hyaluronate solution (SAA + HA group horses, 6). An additional 500 mL of the respective treatment solution was applied to the jejunal serosal surface, and 2 jejunal serosal abrasion sites were created. Horses were euthanatized 10 days after surgery. Anastomoses and abdominal adhesions were evaluated grossly. Anastomotic healing was evaluated on the basis of bursting wall tension. RESULTS: Bursting wall tension was significantly greater in SAA + SCMC group horses, compared with control group horses. All intestinal segments failed at a point distant to the anastomosis. Significantly fewer adhesions were found at the abrasion sites of SAA + HA group horses, compared with control group horses. No differences were found in adhesion formation at the anastomotic sites among groups. CONCLUSIONS AND CLINICAL RELEVANCE: Coating a single-layer appositional jejunal anastomosis with SCMC or HA solutions does not adversely affect anastomotic healing. Application of 0.4% HA solution to the serosal surface of the jejunum significantly decreases the incidence of experimentally induced intra-abdominal adhesion formation in horses.

Effect of topical application of diclofenac liposomal suspension on experimentally induced subcutaneous inflammation in horses.

OBJECTIVE: To determine whether 1% diclofenac liposomal suspension (DLS) ointment would be absorbed transdermally and attenuate experimentally induced subcutaneous inflammation in horses. ANIMALS: 7 healthy adult horses. PROCEDURE: Inflammation was produced by injecting 1% sterile carrageenan into subcutaneously implanted tissue cages 8 hours before (time -8) and at the time of application of test ointment. A crossover design was used. Horses received 1 of 2 treatments (topically administered control or DLS ointments) during 48 hours of carrageenan-induced subcutaneous inflammation. A single application of test ointment (7.2 g) was applied over each tissue cage (time 0). Samples of transudate and blood were collected at -8, 0, 6, 12, 18, 24, 30, 36, and 48 hours. Plasma and transudate diclofenac concentrations were determined by use of high-performance liquid chromatography. Transudate concentrations of prostaglandin E2 (PGE2) were determined with a competitive enzyme immunoassay. RESULTS: DLS was absorbed transdermally. The highest concentration (mean +/- SEM, 76.2 +/- 29 ng/mL) was detectable in tissue-cage fluid within 18 hours after application. Minimal concentrations of diclofenac were detectable in plasma. Application of DLS significantly decreased transudate concentrations of PGE2 at 6 and 30 hours. Decreases in PGE2 concentration were observed in the DLS group at all collection times. CONCLUSIONS AND CLINICAL RELEVANCE: A single topical application of DLS resulted in concentrations of diclofenac in transudate within 6 hours and significantly attenuated carrageenan-induced local production of PGE2. Results of this study suggest that DLS is readily absorbed transdermally and may be efficacious for reducing subcutaneous inflammation in horses.

Prevention and treatment of gastrointestinal adhesions.

As with many aspects of clinical medicine, there is yet to be a single or definitive cure for postoperative adhesion formation. Current methods of prevention target risk factors predisposing horses to adhesion formation. Systemic pharmacologic therapies, such as antimicrobials, nonsteroidal anti-inflammatory drugs, Salmonella antiserum, and hyperimmune plasma, help to reduce abdominal inflammation and minimize the effects of endotoxemia. Intra-abdominal or systemic heparin aids in enhancing peritoneal fibrinolysis. Prokinetic therapy promotes early postoperative return of intestinal motility, minimizing the propensity for adhesion formation between apposing adynamic segments of intestine. Mechanical separation of potentially adhesiogenic serosal and peritoneal surfaces is commonly achieved with use of abdominal lavage, protective coating solutions, and barrier membranes. Ongoing and future research is directed toward a better understanding of the local effects of intestinal trauma and the corresponding response of the fibrinolytic system. Recognition of horses at high risk for adhesion formation helps to guide the equine surgeon to an appropriate perioperative and intraoperative plan for adhesion prevention, including good surgical technique and a combination of adjunct therapies.